It is probably not the transmission. It is most likely the traction control shutting the engie down. It is designed to do this if wheel slip is detected by the traction control system. If it is doing this under normal driving conditions (i.e.
normal speed, dry pavement, no erratic acceleration, etc.) then the traction control system may be malfunctioning. This can be caused by several things, but the most common is a defective/malfunctioning wheel speed sensor that makes the computer "think" that a wheel is slipping when it clearly is not. A way to verify that this is the case, turn your traction control back on and drive the way you normally do. When the problem occurs, pay attention to the "TRAC" light on your dash and see if it is lighting up when the problem occurs. If it does, then the problem is definately being caused by your traction control system.
scan of your Powertrain Control Module (PCM), Antilock Brake System (ABS) module, Instrument Panel Cluster (IPC) module and your Body Control Module (BCM) should be performed to see if it is setting any fault codes. Sometimes the BCM or IPC will report a network communications problem or a speed sensor problem when the other modules show "No Codes Present". Please note that this is NOT something that can be done for "free" by your local auto parts store. These types of codes are not output to a generic OBD code reader.
Please also review this article:
What Else Could Be Wrong?